World

Seawater Could Fuel the Battleships of the Future

The world's supply of petroleum is finite. The U.S. Navy, which runs on it, is not. Eventually, keeping its fleet afloat for generations may depend on another fuel — the kind that doesn't dry up.

Last month, a national-security commission advised Congress to fund shipbuilding and increase the U.S. naval presence in the Asia-Pacific region in the next decade to compete with China's growing fleet. But upping production of petroleum fuel to meet potential future demands is at odds with the Navy's plans to reduce its dependence on the fossil fuel, the deadlines for which are fast approaching. The Department of the Navy has pledged to cut petroleum use in the service's commercial fleet in half by 2015, and produce at least 50% of its jet fuel using alternative sources by 2020.

The Naval Research Laboratory, a 90-year-old corporate research hub serving the Navy and Marine Corps, is searching for such alternative sources. Led by analytical chemist Heather Willauer, the lab is developing technology that sucks up the gases necessary to produce synthetic jet fuel for ships right out of the seawater they tread. If and when it becomes commercially viable, the technology could transform naval operations.

"If they made fuel at sea," Willauer says, "they wouldn't be buying it."

The process begins with a three-chambered cell that receives a stream of seawater in the central compartment. Right now, one of these units sits on the shore of Key West, Fla., at the lab's Center for Corrosion Science & Engineering facility.

The cell pulls a relatively pure and concentrated source of carbon dioxide from the seawater. This source is usually better than carbon dioxide recovered from flue or stack gases produced by the burning of fossil fuels, Willauer says. Such gases require expensive, energy-intensive hardware to further purify them so they're safe to use and won't harm living organisms.

The cell produces hydrogen, which aids in recovering carbon dioxide from seawater. Both processes occur in tandem. The unit captures up to 92% of carbon dioxide from the seawater, where it is 140 times higher in concentration than in the air. All the energy supplied to the cell goes into making hydrogen, not into the extraction process, so the recovered carbon dioxide is actually free, Willauer says.

The lab then uses an iron-based catalyst to convert the gases into olefins, a type of reactive chemical compound. The compound can easily undergo further catalytic conversion into a liquid that contains hydrocarbon molecules, which can eventually be transformed into jet fuel.

This tri-chamber cell eliminates the need for electrolysis units — large and expensive technologies that use electricity to drive chemical reactions producing hydrogen. But even here, hydrogen production uses up a great deal of energy, which increases the amount of carbon in the air. The carbon-capture technology, although more advanced than it was during the research's beginnings in 2007, could still be more efficient, Willauer says.

Willauer and her team have received commercial-scale reactors and other equipment necessary to begin producing up to one liter a day of fuel. Once they've got enough, they can start prepping the new fuel to meet naval flight specifications. In September, the lab produced enough jet fuel to power the flight of a model plane over the Blossom Point military research facility in Maryland (a video of the action is under production). Eventually, the lab will synthesize enough fuel to power something much, much bigger than model planes — Navy vessels.

Jet fuel derived from seawater would cost between $3 and $6 per gallon to produce, which is comparable to current prices of petroleum fuel, Willauer says. "You would have a set price for fuel," she says. "You don't have to worry about foreign markets and this idea that fuel is going to run out."

A viable non-petroleum fuel could help the Navy tackle two problems simultaneously. The technology would be a boon to its alternative energy goals, and would provide a faster and safer process of refueling to its expanding fleet.

Filling up the tank at sea is a costly, time-consuming, and risky venture: Ships have to remain close together, matching each other's speed as they cut through the water, for hours. Last year, an 844-foot Navy assault ship collided with a refueling tanker as they prepared to line up alongside each other to refuel when the assault ship's steering malfunctioned.

Fast-tracking the research, however, requires two things. One, as is often the case in scientific research, is funding, which Willauer calls a "challenging issue." The lab receives funding internally, but outside sponsors, to whom researchers often pitch their projects, can fund the project. The other requirement is simply more time to improve the technology.

Combine more money with more time, Willauer says, and seawater-sourced jet fuel could become a commercial reality in 10 to 15 years. For the Navy, that reality could cut costs, boost security, and help to meet energy goals — all while its fleet continues to compete in international waters.

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